Prescription Dive Masks

CREDITS | Text and photos by Joshua Nowitz

Clear vision is important for more than just enjoying a dive. Not being able to see your gauges or find your way back to the dive boat if separated from the group can be hazardous.

"Accurate vision is essential to overall dive safety," says Dr. Robert Sanders, medical director at the Johnson Space Center's Neutral Buoyancy Laboratory and a specialist in undersea and hyperbaric medicine.

To understand the options for divers who require refractive correction, a basic knowledge of how the eye works is helpful. Light enters through the cornea, where the focusing process begins, and passes through the pupil. The lens further focuses the light onto the retina, where photoreceptors convert the light into electrical signals that move to the optic nerve. In many individuals, the light is not precisely focused on the retina, and this is correctible with prescription lenses. Common conditions include myopia (nearsightedness), hyperopia (farsightedness), presbyopia (difficulty focusing on close objects) and astigmatism (irregular curve of the cornea or lens).

A variety of products are available — including contact lenses, stock-lens masks and custom lenses — that can help improve your vision underwater.

Premade Lenses

Premade or stock-lens dive masks are readily available off the shelf at many dive stores or online. These lenses can correct the sphere (nearsighted or farsighted) portion of your prescription in powers 0 through -8.00 and 0 through +4.00. Purchasing one at a dive store can help ensure a proper fit. Stock-lens masks are an excellent option for divers with mild astigmatism (cylinder correction under 0.75) and no other vision issues. Some individuals cannot use stock-lens masks because their spherical correction is greater than what the stock lenses can correct.

Contact Lenses

Contact lenses offer several advantages. They are available in a wide range of prescriptions, including multifocal and astigmatism corrections, and provide uninterrupted corrected vision before, during and after a dive.

"Any water is prone to bacteria," Sanders cautions, "so if you open your eyes underwater when water is in your dive mask, it is always a good idea to remove your contact lenses after the dive and clean them."

There are no current records of how many divers wear contact lenses while diving, but about half of contact lens wearers report swimming while wearing their contacts.1 While rare, complications from contact lenses and water contact can be severe. A study published in the American Journal of Ophthalmology showed that 85 percent of cases of Acanthamoeba keratitis — an infection of the cornea that is caused by a freshwater-residing amoeba and can lead to blindness — were observed in contact lens wearers who wore their lenses while swimming or diving.2

Contact lenses can also be easy to lose. A diver should always carry spare lenses if losing a pair would make diving impossible.

Please consult with an eye care professional before considering wearing contacts while diving to ensure you follow any up-to-date guidelines and recommendations.

Traditional Custom Dive Mask Lenses

Dive mask lenses are typically glass due to its unique scratch resistance and optical clarity. Most prescription dive mask manufacturers that make custom dive mask lenses use glass, but one company in Florida uses polycarbonate or plastic lenses. In general, refractive dive mask lenses come in two varieties: drop-in or laminated. Drop-in lenses are available for a limited prescription range (including astigmatism correction) for some masks. Laminated lenses are installed in a lab, can be applied to any dive mask and can correct for any prescription, including prism lenses for divers suffering from double vision.

Custom dive mask lenses are produced in your exact prescription and can correct even very large refractive errors caused by nearsightedness, farsightedness and astigmatism, ensuring the highest visual acuity underwater. High-index glass lenses can reduce the lens thickness and provide sharper edge-to-edge clarity for divers with stronger prescriptions.

Reading Lenses or Bifocals

Almost all divers will develop presbyopia to some extent as they age due to the decreasing ability of the eye's aging lens to focus on near objects. Some older people will have either nearsightedness or farsightedness along with their presbyopia, which will require both distance and near correction. There are various ways to address these issues while diving. Some dive mask lenses have a part of the lens that corrects only for near vision. These premade "gauge reader" dive masks are available to assist in reading gauges and dive computers. Divers who need a specific reading power or want a larger reading glass size for photography should consider having custom reading lenses permanently installed in their masks. Over-the-counter stick-on reading lenses are available at most dive stores.

A Franklin bifocal mask is the most expensive option for near and distance correction. With two separate segments per eye, the diver can choose how much space they require for distance and close vision. A diver can choose to have 70 percent of the mask for near vision, for example, if they spend most of their time looking at a video monitor during professional underwater shoots. While progressive (no-line bifocal) lenses for dive masks are possible, they are expensive and provide little benefit to the diver because the intermediate distance is less valuable underwater, and issues with lens placement can cause more problems with progressive lenses than with traditional lens designs.

Any quality dive mask can have prescription lenses installed, but not every dive mask is ideal for every prescription. The thickness of a corrective lens is a factor of the strength of the prescription, surface area of the lens and decentration (in nonoptical terms, where the diver's pupil sits in the lens versus the geometric center of the lens). High-plus spherical lenses are convex and extend toward the center of the diver's eye, so divers needing high-plus correction should steer toward masks with enough volume to ensure the lenses don't contact their face.

Divers must also have backup options based on their diving and corrective needs. If the lack of a backup means the loss of liveaboard dives or photo shoots, it may be worthwhile to have an extra prescription mask. Divers who wear contact lenses should always have a pair of glasses available should they lose a contact or if the contacts cause irritation.

Whichever corrective option a diver chooses, being able to see clearly will improve the quality and safety of every dive.

**Joshua Nowitz is an optical technician and owner of a prescription dive mask manufacturer. He is a PADI instructor and has been involved in diving for more than 20 years. He has also worked as a sergeant at the Harris County, Texas, Sheriff's Office, which included time as the instructor for the dive team.
© Alert Diver — Q2 2020